The Fewest Given Digits possible in a Sudoku ...

Normal sudoku rules apply. The digits before an equals sign have the same sum as the digits after, and the equation includes X in the first or last cell of the row/column, where X is the total number of digits used in the equation.

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▶Music◀
Tim McCaskey (Guitar) or Lucy Audrin (Piano) or Riffclown plays Mozart's Sonata no 16 ("Sonata Facile")
▶SOFTWARE◀
Play the puzzle in the video by clicking the link under the video (above). Thanks to Sam Cappleman-Lynes and Sven Neumann for their work.
▶Logo Design◀
Melvyn Mainini

▶Opening Credits Design◀
Joel Blundell

▶ABOUT US◀
Hi! We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships. We're also "cryptic crossword" aficionados. Mark is the twelve-time winner of The Times championship and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.

Thank you for watching!
Simon and Mark

[oddgarrett]

Mark: "I wish I had a way of notating which equals signs I'd done, but I don't think that's easy"
The Pen tool: *sits quietly in the corner*

[robtheslob]

I like to think I'm a clever person.... then I come

[sampathkumar-ejxl]

A great puzzle which unravelled ever so slowly for me with all those number combinations. What fantastic setters have emerged from around the world!

[omursatik]

Great deduction around the 25 min mark. Don’t think I would have got that in a month of Sundays. Well done Mark

[piarittersporn]

Although I had to delete most of my digits several times and my head was already quite confused, I could not resist the challenge and had to try again and again. After more than two (!!) hours finally I was able to compare my solution with Mark's and was satisfied and happy. A great puzzle.

[gonzodpc]

Mark, you can mark the equal sign marks with an X mark with the pen tool - Full Marks, great puzzle!

[joana_drb]

Really nice puzzle again today! I didn’t try it cause i could never even get started but watching you solve it was an absolute pleasure! Great job as always 👍

[inspiringsand]

Rules: 02:49
Let's Get Cracking: 04:31
Mark's time: 37m34s
Puzzle Solved: 42:05

What about this video's Top Tier Simarkisms?!
Cooking with Gas: 1x (33:55)
The Secret: 1x (08:09)

And how about this video's Simarkisms?!
Ah: 10x (07:53, 12:01, 16:52, 17:33, 22:06, 22:52, 27:40, 29:32, 29:39, 33:22)
Brilliant: 6x (26:07, 26:10, 31:51, 41:01, 42:24, 42:26)
Obviously: 5x (02:38, 07:56, 07:56, 11:38, 20:57)
Sorry: 4x (37:40, 38:58, 39:15, 40:53)
Beautiful: 4x (17:04, 27:02, 28:56, 28:57)
By Sudoku: 3x (06:20, 15:10, 17:46)
In Fact: 3x (09:27, 24:03, 40:38)
Wow: 3x (26:07, 27:18, 31:25)
Clever: 2x (27:23, 41:03)
Fascinating: 2x (04:16, 23:21)
What Does This Mean?: 2x (12:31, 23:34)
Nonsense: 1x (15:22)
Stuck: 1x (23:17)
Shouting: 1x (22:10)
Hang On: 1x (18:22)
Bizarre: 1x (42:15)
Surely: 1x (04:57)
Progress: 1x (16:31)
Gobsmacked: 1x (41:13)
Have a Think: 1x (37:28)
Pencil Mark/mark: 1x (14:36)

Most popular number(>9), digit and colour this video:
Thirteen (24 mentions)
Seven (97 mentions)
Green (3 mentions)

Antithesis Battles:
Low (2) - High (0)
Odd (15) - Even (5)
Higher (2) - Lower (2)
Row (26) - Column (14)

FAQ:
Q1: You missed something!
A1: That could very well be the case! Human speech can be hard to understand for computers like me! Point out the ones that I missed and maybe I'll learn!
Q2: Can you do this for another channel?
A2: I've been thinking about that and wrote some code to make that possible. Let me know which channel you think would be a good fit!

[edhunterofmaidengrad]

This took me FOREVER. Like several days going back to it on and off during my work day. But I'm glad I stuck with it! It's tough logic but very satisfying.

[emilywilliams]

Sometimes I can tell that there is a measure of politeness in praising a puzzle while solving it. But tonight I sensed that you genuinely had fun, Mark, and found it very interesting and entertaining. As did I! Will I try this puzzle later? Well, maybe I will ... but nevertheless, I enjoyed watching your video (as always). A couple of things I will quote here, because they made me smile or even laugh: about the relative usefulness of the x-wing on 3s, I think it was, "I enjoyed it, and that's the key thing." Yes, that is absolutely true. When you enjoy solving a puzzle, even if there are some aspects of how you go about it that may be not as efficient as might be, that is good. I love seeing you have fun, and I am sure that this is one of the things about this channel that appeals to so many of us. The second thing, which I totally loved and laughed at: "... maths juggling, that makes people either alternatively gobsmacked or just appalled that I think this is fun ..." I do get it! I love it too - but you are particularly good at keeping in your head. Amazing. (And the word 'gobsmacked' is an excellent word.) Thank you! (Oh one more thing: this was a longer-than-average video for you, I think, Mark, but it seemed like a speed solve after The Masterpiece that Simon premiered earlier today, especially since I watched that one twice! What a day at CTC!)

[Swisswavey]

The rule set was a bit confusing but it was a refreshing change just to watch you solve it. The shenanigans in rows 1&3 would have stumped me so I'm glad I avoided that. A really impressive solve, well done.

[brucejones]

That was an amazing solve! Nice work, so evident when you really enjoy the logic required to figure out the puzzle.

[Coyotek]

49:18 ... this one was absolutely BONKERS! [I mean that as a compliment, btw.]

Crazy puzzle!

[davidblake]

Mark, I didn't have a problem with the rules. But I had a problem with what to do with them. Thanks for the solve, it showed me how the solution path works. Great solve. Thanks.

[richardcapstack]

I can understand why Simon’s solves receive more hits- he gives one more time to think the problem through, however, Mark is, in my opinion, the finer solver.

[SpeedyBozar]

I like these kinds of rules. And this in particular was a nice twist, I like it a lot.

[lukas-oqyh]

“do give it a try”
*takes 30 minutes to finish a classic hard sudoku*
no mark thank you, i’ll sit this one out you can do it alone😊

[JohnRandomness]

22:20 I have that cell (R9C6) as very low. On the other hand, I've currently broken the puzzle.
29:00 I'm gratified that so far, Mark's results have exactly matched mine so far, even if his logic is more robust.
35:55 Still echoing what I have. Still gratified, still wondering where I went wrong.
36:20 A 9 x-wing fixes the 9 in the orange column.
38:30 I've had a 54 in R4C2, where he's just penciled 568. It's been there for the longest time. It's where my 94 in the domino at the end of the row broke the puzzle. Therefore... (That domino will appear in the video once he spots the 9 x-wing.)
39:45 Ha! He found it!

It was quite a relief that nothing but an old pencilmarked cell stalled me there. I had just placed the 4 next to the 9, and gone to check that row's sums, and found myself unable to add to to sixteen. Recovering fortunately meant only fixing the pencilmarks.

[linforcer]

2:35:54 Which is a bit faster than I usually do when there is a 40 minute video... what's really interesting to me is that I actually had rows 7 and 8 filled in before 5 and 6

[ChilapaOfTheAmazons]

Well, it took me 68 minutes but I managed to solve it.

Really enjoyable puzzle. ✌️😁